Phosphate ion functionalized Co3O4 nanosheets/RGO with improved electrochemical performance

Abstract

By using surfactants P123 as directional growth agent of Co(OH)2 nanosheets, Co3O4 nanosheet/reduced graphite oxide (RGO) hybrid material was prepared by calcining precursor Co(OH)2/graphite oxide (GO) at 275 °C for 2 h and followed by thermal annealing at 500 °C for 1.5 h in Ar atmosphere. With a mass ratio of Co3O4/RGO to NaH2PO2·H2O being 10, phosphate-ion functionalized Co3O4 nanosheets/RGO (denoted as P-Co3O4/RGO-10) was finally prepared by phosphating treating Co3O4/RGO at 225 °C for 30 min. The phase transition from Co(OH)2 nanosheets to Co3O4 nanosheets was a topochemical process and Co3O4 nanosheets with porous characteristic were uniformly dispersed on the surface of RGO. Phosphating treatment not only improved the surface reaction activity of Co3O4 nanosheets and rate performance of the obtained electrode materials, but also caused thin nanosheet pores favorable to the transport of electrolyte ions. P-Co3O4/RGO-10 hybrid electrode showed improved specific capacitance (448 F g-1) at a current density of 1 A g-1, extremely outstanding rate capability (78 %) at various current densities from 1 to 10 A g-1 and good cycling performance after continuous 5000 cycles. Phosphating treatment technology is an effective surface engineering technology to improve rate capability and specific capacitance for pseudocapacitive materials.